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Any website that lists OS compatible with Raspberry Pi 0 W running ARM V6
(discuss.tchncs.de)
Projekte rund um den Raspberry PI
Not sure it counts as a separate OS, but I run DietPi on all of my pi's. It's a super stripped down version of Debian/RPiOS. Everything you need, nothing you don't.
DietPi is great, I also run it on all my devices. Highly recommended!